Uni-Penetration Tendon Retention and Fill Port System for a Balloon Envelope

ABSTRACT

Methods and apparatus are disclosed for an apex fitting for securing to a high altitude balloon. An example apparatus involves: (a) a base plate defining an opening, where the base plate is configured to be securable to an exterior of a balloon envelope, (b) at least one stud coupled to the base plate and configured to be securable to a tendon, (c) a retention ring defining at least one opening configured to receive the at least one stud, (d) a fill-port body defining a cavity, wherein a flange is coupled to the fill-port body, wherein the fill-port body is arranged coaxially with and extends through the opening of the base plate such that the flange lies adjacent to the bottom surface of the base plate, and (e) a locking body coupled to the fill-port body, wherein the locking body defines an opening arranged coaxially with the fill-port body.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the filing date of U.S.Non-Provisional patent application Ser. No. 14/153,020, filed Jan. 11,2014, which is hereby incorporated by reference in its entirety.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Computing devices such as personal computers, laptop computers, tabletcomputers, cellular phones, and countless types of Internet-capabledevices are increasingly prevalent in numerous aspects of modern life.As such, the demand for data connectivity via the Internet, cellulardata networks, and other such networks, is growing. However, there aremany areas of the world where data connectivity is still unavailable, orif available, is unreliable and/or costly. Accordingly, additionalnetwork infrastructure is desirable.

SUMMARY

An apex fitting described herein advantageously provides a base plateconfigured to be securable to the exterior of a balloon envelope via asingle perforation through the balloon envelope. This arrangement mayminimize air leaks from the balloon envelope. In addition, the baseplate may be beneficially configured to be coupled to a retention ringwithout perforating the balloon envelope. The retention ring may furtherhold tendons in place at the apex of the balloon envelope. In addition,a fill-port body may be advantageously coupled to the base plate, ratherthan being coupled to the soft balloon envelope, to remove stress fromthe balloon envelope.

In one aspect, an example apparatus involves: (a) a base plate having atop surface and a bottom surface, wherein the base plate defines anopening, and wherein the base plate is configured to be securable to anexterior of a balloon envelope, (b) at least one stud coupled to thebase plate, wherein the at least one stud is configured to be securableto a tendon, (c) a retention ring defining at least one openingconfigured to receive the at least one stud, (d) a fill-port bodydefining a cavity, wherein a flange is coupled to the fill-port body,wherein the fill-port body is arranged coaxially with and extendsthrough the opening of the base plate such that the flange lies adjacentto the bottom surface of the base plate, and (e) a locking body coupledto the fill-port body, wherein the locking body defines an openingarranged coaxially with the fill-port body, wherein the fill-port bodyextends through the opening of the locking body such that a portion ofthe locking body lies adjacent to the top surface of the base plate.

In another aspect, an example method involves: (a) affixing a base plateto a balloon envelope, wherein the balloon envelope defines an openingat an apex of the balloon envelope, wherein the base plate defines anopening, wherein the opening of the base plate is aligned with theopening of the balloon envelope, and wherein a plurality of studs arecoupled to the base plate, (b) placing a fill-port body through theopening of the balloon envelope and through the opening of the baseplate such that a flange of the fill-port body lies adjacent to theballoon envelope, (c) securing a locking body to the fill-port bodyand/or the base plate such that the locking body lies adjacent to thebase plate, (d) securing a plurality of tendons to the plurality ofstuds, and (e) securing a retention ring to the base plate.

In a further aspect, a balloon is provided having a balloon envelope andmeans for retaining tendons at the apex of a balloon envelope and meansfor filling the balloon envelope with air.

These as well as other aspects, advantages, and alternatives, willbecome apparent to those of ordinary skill in the art by reading thefollowing detailed description, with reference where appropriate to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram illustrating a balloon network, accordingto an example embodiment.

FIG. 2 is a diagram illustrating a balloon-network control system,according to an example embodiment.

FIG. 3 is a simplified diagram illustrating a high-altitude balloon,according to an example embodiment.

FIG. 4 is a simplified diagram illustrating a balloon network thatincludes super-nodes and sub-nodes, according to an example embodiment.

FIG. 5A is a perspective view of an example apparatus, according to anexample embodiment.

FIG. 5B is a detail view of the example apparatus shown in FIG. 5A.

FIG. 6A is a cross-sectional side view of the example apparatus shown inFIG. 5A.

FIG. 6B is a detail cross-sectional side view a fill-port body of theexample apparatus shown in FIG. 6A.

FIG. 6C is a detail cross-sectional side view of an example locking pinof the example apparatus shown in FIG. 6A.

FIG. 6D is a detail cross-sectional side view of an example stud of theexample apparatus shown in FIG. 6A.

FIG. 7 shows a high-altitude balloon, according to an exampleembodiment.

FIG. 8 is a flow chart of a method according to an example embodiment.

DETAILED DESCRIPTION

Example methods and systems are described herein. Any example embodimentor feature described herein is not necessarily to be construed aspreferred or advantageous over other embodiments or features. Theexample embodiments described herein are not meant to be limiting. Itwill be readily understood that certain aspects of the disclosed systemsand methods can be arranged and combined in a wide variety of differentconfigurations, all of which are contemplated herein.

Furthermore, the particular arrangements shown in the Figures should notbe viewed as limiting. It should be understood that other embodimentsmay include more or less of each element shown in a given Figure.Further, some of the illustrated elements may be combined or omitted.Yet further, an example embodiment may include elements that are notillustrated in the Figures.

1. OVERVIEW

Example embodiments disclosed herein may generally relate to a datanetwork formed by balloons, and in particular, to a mesh network formedby high-altitude balloons deployed in the stratosphere. In someapplications, it may be desirable for high altitude balloons to retainlift gas for one hundred days or more. Example balloons may beconfigured to have a top chamber to receive and retain lift gas and abottom chamber to receive and retain air. In one embodiment, neitherchamber may initially contain perforations, but a hole may be defined inthe balloon envelope to receive a fill port to administer lift gas andfill the balloon envelope. The present invention may also be used withballoons that are made of a number of gores seamed together resulting inholes at the apex and base of the balloon, for example, among otherpossibilities.

Example embodiments may advantageously provide a single perforation inthe top chamber of the balloon envelope. This advantage may beaccomplished by relocating the rigid fill port from the soft film of theballoon to a rigid base plate at the apex of the balloon envelope suchthat the fill port is the only perforation in the balloon envelope incommunication with lift gas. Placing the fill port in the base platebeneficially removes stress from the balloon envelope.

In addition, example embodiments may advantageously provide a base platethat may be securable to the exterior of a balloon envelope via thesingle perforation. For example, the base plate may be initially securedto the balloon envelope via tape or adhesive. The base plate may definea plurality of studs configured to be coupled to the ends of a pluralityof tendons. The opposite ends of the plurality of tendons may be coupledto a fitting on the underside of the balloon for film-load assistancewhen the balloon is pressurized. Once the balloon is pressurized,friction between the tendons and the outward pressing envelope may begreat enough to hold the apex fitting in place. Known apex fittingstypically have over forty perforations in the balloon envelope and thebase plate. Each perforation is a source for potential air leaks fromthe balloon envelope. Thus, the single perforation of the presentinvention has the benefit of minimizing air leaks.

To ensure the tendons stay in place, a retention ring may be coupled tothe base plate, such that the tendon loops are sandwiched in between thebase plate and the retention ring. The retention ring defines aplurality of openings configured to receive the plurality of studs. Eachstud may have a body and a flange coupled to the free end of the body.The plurality of openings in the retention ring may each have a firstportion sized to receive the flange of a corresponding stud and a secondportion defining a channel having a width narrower than a diameter ofthe flange. This arrangement allows the first portion of the openings toslide over the flange of the studs and down to the body of the studs.The retention ring may then be rotated such that the body of the studsis received in the second portion of the openings, locking the retentionring in place. One or more locking pins may then be disposed through theretention ring to prevent the retention ring from rotating to anunlocked position.

In some embodiments, the base plate may define one or more apertures orwindows therein, which advantageously reduces the weight of the apexfitting. In addition, the base plate may beneficially include electricalpassages for coupling to one or more sensors.

2. EXAMPLE BALLOON NETWORKS

In an example balloon network, the balloons may communicate with oneanother using free-space optical communications. For instance, theballoons may be configured for optical communications using ultra-brightLEDs (which are also referred to as “high-power” or “high-output” LEDs).In some instances, lasers could be used instead of or in addition toLEDs, although regulations for laser communications may restrict laserusage. In addition, the balloons may communicate with ground-basedstation(s) using radio-frequency (RF) communications.

In some embodiments, a high-altitude-balloon network may be homogenous.That is, the balloons in a high-altitude-balloon network could besubstantially similar to each other in one or more ways. Morespecifically, in a homogenous high-altitude-balloon network, eachballoon is configured to communicate with nearby balloons via free-spaceoptical links. Further, some or all of the balloons in such a network,may also be configured to communicate with ground-based station(s) usingRF communications. (Note that in some embodiments, the balloons may behomogenous in so far as each balloon is configured for free-spaceoptical communication with other balloons, but heterogeneous with regardto RF communications with ground-based stations.)

In other embodiments, a high-altitude-balloon network may beheterogeneous, and thus may include two or more different types ofballoons. For example, some balloons may be configured as super-nodes,while other balloons may be configured as sub-nodes. Some balloons maybe configured to function as both a super-node and a sub-node. Suchballoons may function as either a super-node or a sub-node at aparticular time, or, alternatively, act as both simultaneously dependingon the context. For instance, an example balloon could aggregate searchrequests of a first type to transmit to a ground-based station. Theexample balloon could also send search requests of a second type toanother balloon, which could act as a super-node in that context.

In such a configuration, the super-node balloons may be configured tocommunicate with nearby super-node balloons via free-space opticallinks. However, the sub-node balloons may not be configured forfree-space optical communication, and may instead be configured for someother type of communication, such as RF communications. In that case, asuper-node may be further configured to communicate with sub-nodes usingRF communications. Thus, the sub-nodes may relay communications betweenthe super-nodes and one or more ground-based stations using RFcommunications. In this way, the super-nodes may collectively functionas backhaul for the balloon network, while the sub-nodes function torelay communications from the super-nodes to ground-based stations.Other differences could be present between balloons in a heterogeneousballoon network.

FIG. 1 is a simplified diagram illustrating a balloon network 100,according to an example embodiment. As shown, balloon network 100includes balloons 102A to 102F, which are configured to communicate withone another via free-space optical links 104. Balloons 102A to 102Fcould additionally or alternatively be configured to communicate withone another via RF links 114. Balloons 102A to 102F may collectivelyfunction as a mesh network for packet-data communications. Further,balloons 102A to 102F may be configured for RF communications withground-based stations 106 and 112 via RF links 108. In another exampleembodiment, balloons 102A to 102F could be configured to communicate viaoptical link 110 with ground-based station 112.

In an example embodiment, balloons 102A to 102F are high-altitudeballoons, which are deployed in the stratosphere. At moderate latitudes,the stratosphere includes altitudes between approximately 10 kilometers(km) and 50 km altitude above the surface. At the poles, thestratosphere starts at an altitude of approximately 8 km. In an exampleembodiment, high-altitude balloons may be generally configured tooperate in an altitude range within the stratosphere that has lowerwinds (e.g., between 5 and 20 miles per hour (mph)).

More specifically, in a high-altitude-balloon network, balloons 102A to102F may generally be configured to operate at altitudes between 17 kmand 25 km (although other altitudes are possible). This altitude rangemay be advantageous for several reasons. In particular, this layer ofthe stratosphere generally has mild wind and turbulence (e.g., windsbetween 5 and 20 miles per hour (mph)). Further, while the winds between17 km and 25 km may vary with latitude and by season, the variations canbe modelled in a reasonably accurate manner. Additionally, altitudesabove 17 km are typically above the maximum flight level designated forcommercial air traffic. Therefore, interference with commercial flightsis not a concern when balloons are deployed between 17 km and 25 km.

To transmit data to another balloon, a given balloon 102A to 102F may beconfigured to transmit an optical signal via an optical link 104. In anexample embodiment, a given balloon 102A to 102F may use one or morehigh-power light-emitting diodes (LEDs) to transmit an optical signal.Alternatively, some or all of balloons 102A to 102F may include lasersystems for free-space optical communications over optical links 104.Other types of free-space optical communication are possible. Further,in order to receive an optical signal from another balloon via anoptical link 104, a given balloon 102A to 102F may include one or moreoptical receivers. Additional details of example balloons are discussedin greater detail below, with reference to FIG. 3.

In a further aspect, balloons 102A to 102F may utilize one or more ofvarious different RF air-interface protocols for communicationground-based stations 106 and 112 via RF links 108. For instance, someor all of balloons 102A to 102F may be configured to communicate withground-based stations 106 and 112 using protocols described in IEEE802.11 (including any of the IEEE 802.11 revisions), various cellularprotocols such as GSM, CDMA, UMTS, EV-DO, WiMAX, and/or LTE, and/or oneor more propriety protocols developed for balloon-to-ground RFcommunication, among other possibilities.

In a further aspect, there may scenarios where RF links 108 do notprovide a desired link capacity for balloon-to-ground communications.For instance, increased capacity may be desirable to provide backhaullinks from a ground-based gateway, and in other scenarios as well.Accordingly, an example network may also include downlink balloons,which could provide a high-capacity air-ground link.

For example, in balloon network 100, balloon 102F could be configured asa downlink balloon. Like other balloons in an example network, adownlink balloon 102F may be operable for optical communication withother balloons via optical links 104. However, downlink balloon 102F mayalso be configured for free-space optical communication with aground-based station 112 via an optical link 110. Optical link 110 maytherefore serve as a high-capacity link (as compared to an RF link 108)between the balloon network 100 and a ground-based station 112.

Note that in some implementations, a downlink balloon 102F mayadditionally be operable for RF communication with ground-based stations106. In other cases, a downlink balloon 102F may only use an opticallink for balloon-to-ground communications. Further, while thearrangement shown in FIG. 1 includes just one downlink balloon 102F, anexample balloon network can also include multiple downlink balloons. Onthe other hand, a balloon network can also be implemented without anydownlink balloons.

In other implementations, a downlink balloon may be equipped with aspecialized, high-bandwidth RF communication system forballoon-to-ground communications, instead of, or in addition to, afree-space optical communication system. The high-bandwidth RFcommunication system may take the form of an ultra-wideband system,which provides an RF link with substantially the same capacity as theoptical links 104. Other forms are also possible.

Balloons could be configured to establish a communication link withspace-based satellites in addition to, or as an alternative to, aground-based communication link.

Ground-based stations, such as ground-based stations 106 and/or 112, maytake various forms. Generally, a ground-based station may includecomponents such as transceivers, transmitters, and/or receivers forcommunication via RF links and/or optical links with a balloon network.Further, a ground-based station may use various air-interface protocolsin order communicate with a balloon 102A to 102F over an RF link 108. Assuch, ground-based stations 106 and 112 may be configured as an accesspoint with which various devices can connect to balloon network 100.Ground-based stations 106 and 112 may have other configurations and/orserve other purposes without departing from the scope of the invention.

Further, some ground-based stations, such as ground-based stations 106and 112, may be configured as gateways between balloon network 100 andone or more other networks. Such ground-based stations 106 and 112 maythus serve as an interface between the balloon network and the Internet,a cellular service provider's network, and/or other types of networks.Variations on this configuration and other configurations ofground-based stations 106 and 112 are also possible.

2a) Mesh Network Functionality

As noted, balloons 102A to 102F may collectively function as a meshnetwork. More specifically, since balloons 102A to 102F may communicatewith one another using free-space optical links, the balloons maycollectively function as a free-space optical mesh network.

In a mesh-network configuration, each balloon 102A to 102F may functionas a node of the mesh network, which is operable to receive datadirected to it and to route data to other balloons. As such, data may berouted from a source balloon to a destination balloon by determining anappropriate sequence of optical links between the source balloon and thedestination balloon. These optical links may be collectively referred toas a “lightpath” for the connection between the source and destinationballoons. Further, each of the optical links may be referred to as a“hop” on the lightpath.

To operate as a mesh network, balloons 102A to 102F may employ variousrouting techniques and self-healing algorithms. In some embodiments, aballoon network 100 may employ adaptive or dynamic routing, where alightpath between a source and destination balloon is determined andset-up when the connection is needed, and released at a later time.Further, when adaptive routing is used, the lightpath may be determineddynamically depending upon the current state, past state, and/orpredicted state of the balloon network.

In addition, the network topology may change as the balloons 102A to102F move relative to one another and/or relative to the ground.Accordingly, an example balloon network 100 may apply a mesh protocol toupdate the state of the network as the topology of the network changes.For example, to address the mobility of the balloons 102A to 102F,balloon network 100 may employ and/or adapt various techniques that areemployed in mobile ad hoc networks (MANETs). Other examples are possibleas well.

In some implementations, a balloon network 100 may be configured as atransparent mesh network. More specifically, in a transparent balloonnetwork, the balloons may include components for physical switching thatis entirely optical, without any electrical involved in physical routingof optical signals. Thus, in a transparent configuration with opticalswitching, signals travel through a multi-hop lightpath that is entirelyoptical.

In other implementations, the balloon network 100 may implement afree-space optical mesh network that is opaque. In an opaqueconfiguration, some or all balloons 102A to 102F may implementoptical-electrical-optical (OEO) switching. For example, some or allballoons may include optical cross-connects (OXCs) for OEO conversion ofoptical signals. Other opaque configurations are also possible.Additionally, network configurations are possible that include routingpaths with both transparent and opaque sections.

In a further aspect, balloons in an example balloon network 100 mayimplement wavelength division multiplexing (WDM), which may help toincrease link capacity. When WDM is implemented with transparentswitching, physical lightpaths through the balloon network may besubject to the “wavelength continuity constraint.” More specifically,because the switching in a transparent network is entirely optical, itmay be necessary to assign the same wavelength for all optical links ona given lightpath.

An opaque configuration, on the other hand, may avoid the wavelengthcontinuity constraint. In particular, balloons in an opaque balloonnetwork may include the OEO switching systems operable for wavelengthconversion. As a result, balloons can convert the wavelength of anoptical signal at each hop along a lightpath. Alternatively, opticalwavelength conversion could take place at only selected hops along thelightpath.

Further, various routing algorithms may be employed in an opaqueconfiguration. For example, to determine a primary lightpath and/or oneor more diverse backup lightpaths for a given connection, exampleballoons may apply or consider shortest-path routing techniques such asDijkstra's algorithm and k-shortest path, and/or edge and node-diverseor disjoint routing such as Suurballe's algorithm, among others.Additionally or alternatively, techniques for maintaining a particularQuality of Service (QoS) may be employed when determining a lightpath.Other techniques are also possible.

2b) Station-Keeping Functionality

In an example embodiment, a balloon network 100 may implementstation-keeping functions to help provide a desired network topology.For example, station-keeping may involve each balloon 102A to 102Fmaintaining and/or moving into a certain position relative to one ormore other balloons in the network (and possibly in a certain positionrelative to the ground). As part of this process, each balloon 102A to102F may implement station-keeping functions to determine its desiredpositioning within the desired topology, and if necessary, to determinehow to move to the desired position.

The desired topology may vary depending upon the particularimplementation. In some cases, balloons may implement station-keeping toprovide a substantially uniform topology. In such cases, a given balloon102A to 102F may implement station-keeping functions to position itselfat substantially the same distance (or within a certain range ofdistances) from adjacent balloons in the balloon network 100.

In other cases, a balloon network 100 may have a non-uniform topology.For instance, example embodiments may involve topologies where balloonsare distributed more or less densely in certain areas, for variousreasons. As an example, to help meet the higher bandwidth demands thatare typical in urban areas, balloons may be clustered more densely overurban areas. For similar reasons, the distribution of balloons may bedenser over land than over large bodies of water. Many other examples ofnon-uniform topologies are possible.

In a further aspect, the topology of an example balloon network may beadaptable. In particular, station-keeping functionality of exampleballoons may allow the balloons to adjust their respective positioningin accordance with a change in the desired topology of the network. Forexample, one or more balloons could move to new positions to increase ordecrease the density of balloons in a given area. Other examples arepossible.

In some embodiments, a balloon network 100 may employ an energy functionto determine if and/or how balloons should move to provide a desiredtopology. In particular, the state of a given balloon and the states ofsome or all nearby balloons may be input to an energy function. Theenergy function may apply the current states of the given balloon andthe nearby balloons to a desired network state (e.g., a statecorresponding to the desired topology). A vector indicating a desiredmovement of the given balloon may then be determined by determining thegradient of the energy function. The given balloon may then determineappropriate actions to take in order to effectuate the desired movement.For example, a balloon may determine an altitude adjustment oradjustments such that winds will move the balloon in the desired manner.

2c) Control of Balloons in a Balloon Network

In some embodiments, mesh networking and/or station-keeping functionsmay be centralized. For example, FIG. 2 is a diagram illustrating aballoon-network control system, according to an example embodiment. Inparticular, FIG. 2 shows a distributed control system, which includes acentral control system 200 and a number of regional control-systems 202Ato 202B. Such a control system may be configured to coordinate certainfunctionality for balloon network 204, and as such, may be configured tocontrol and/or coordinate certain functions for balloons 206A to 206I.

In the illustrated embodiment, central control system 200 may beconfigured to communicate with balloons 206A to 206I via number ofregional control systems 202A to 202C. These regional control systems202A to 202C may be configured to receive communications and/oraggregate data from balloons in the respective geographic areas thatthey cover, and to relay the communications and/or data to centralcontrol system 200. Further, regional control systems 202A to 202C maybe configured to route communications from central control system 200 tothe balloons in their respective geographic areas. For instance, asshown in FIG. 2, regional control system 202A may relay communicationsand/or data between balloons 206A to 206C and central control system200, regional control system 202B may relay communications and/or databetween balloons 206D to 206F and central control system 200, andregional control system 202C may relay communications and/or databetween balloons 206G to 206I and central control system 200.

In order to facilitate communications between the central control system200 and balloons 206A to 206I, certain balloons may be configured asdownlink balloons, which are operable to communicate with regionalcontrol systems 202A to 202C. Accordingly, each regional control system202A to 202C may be configured to communicate with the downlink balloonor balloons in the respective geographic area it covers. For example, inthe illustrated embodiment, balloons 206A, 206F, and 206I are configuredas downlink balloons. As such, regional control systems 202A to 202C mayrespectively communicate with balloons 206A, 206F, and 206I via opticallinks 206, 208, and 210, respectively.

In the illustrated configuration, where only some of balloons 206A to206I are configured as downlink balloons, the balloons 206A, 206F, and206I that are configured as downlink balloons may function to relaycommunications from central control system 200 to other balloons in theballoon network, such as balloons 206B to 206E, 206G, and 206H. However,it should be understood that it in some implementations, it is possiblethat all balloons may function as downlink balloons. Further, while FIG.2 shows multiple balloons configured as downlink balloons, it is alsopossible for a balloon network to include only one downlink balloon.

Note that a regional control system 202A to 202C may in fact just be aparticular type of ground-based station that is configured tocommunicate with downlink balloons (e.g. the ground-based station 112 ofFIG. 1). Thus, while not shown in FIG. 2, a control system may beimplemented in conjunction with other types of ground-based stations(e.g., access points, gateways, etc.).

In a centralized control arrangement, such as that shown in FIG. 2, thecentral control system 200 (and possibly regional control systems 202Ato 202C as well) may coordinate certain mesh-networking functions forballoon network 204. For example, balloons 206A to 206I may send thecentral control system 200 certain state information, which the centralcontrol system 200 may utilize to determine the state of balloon network204. The state information from a given balloon may include locationdata, optical-link information (e.g., the identity of other balloonswith which the balloon has established an optical link, the bandwidth ofthe link, wavelength usage and/or availability on a link, etc.), winddata collected by the balloon, and/or other types of information.Accordingly, the central control system 200 may aggregate stateinformation from some or all the balloons 206A to 206I in order todetermine an overall state of the network.

The overall state of the network may then be used to coordinate and/orfacilitate certain mesh-networking functions such as determininglightpaths for connections. For example, the central control system 200may determine a current topology based on the aggregate stateinformation from some or all the balloons 206A to 206I. The topology mayprovide a picture of the current optical links that are available in theballoon network and/or the wavelength availability on the links. Thistopology may then be sent to some or all of the balloons so that arouting technique may be employed to select appropriate lightpaths (andpossibly backup lightpaths) for communications through the balloonnetwork 204.

In a further aspect, the central control system 200 (and possiblyregional control systems 202A to 202C as well) may also coordinatecertain station-keeping functions for balloon network 204. For example,the central control system 200 may input state information that isreceived from balloons 206A to 206I to an energy function, which mayeffectively compare the current topology of the network to a desiredtopology, and provide a vector indicating a direction of movement (ifany) for each balloon, such that the balloons can move towards thedesired topology. Further, the central control system 200 may usealtitudinal wind data to determine respective altitude adjustments thatmay be initiated to achieve the movement towards the desired topology.The central control system 200 may provide and/or support otherstation-keeping functions as well.

FIG. 2 shows a distributed arrangement that provides centralizedcontrol, with regional control systems 202A to 202C coordinatingcommunications between a central control system 200 and a balloonnetwork 204. Such an arrangement may be useful to provide centralizedcontrol for a balloon network that covers a large geographic area. Insome embodiments, a distributed arrangement may even support a globalballoon network that provides coverage everywhere on earth. Adistributed-control arrangement may be useful in other scenarios aswell.

Further, it should be understood that other control-system arrangementsare possible. For instance, some implementations may involve acentralized control system with additional layers (e.g., sub-regionsystems within the regional control systems, and so on). Alternatively,control functions may be provided by a single, centralized, controlsystem, which communicates directly with one or more downlink balloons.

In some embodiments, control and coordination of a balloon network maybe shared between a ground-based control system and a balloon network tovarying degrees, depending upon the implementation. In fact, in someembodiments, there may be no ground-based control systems. In such anembodiment, all network control and coordination functions may beimplemented by the balloon network itself. For example, certain balloonsmay be configured to provide the same or similar functions as centralcontrol system 200 and/or regional control systems 202A to 202C. Otherexamples are also possible.

Furthermore, control and/or coordination of a balloon network may bede-centralized. For example, each balloon may relay state informationto, and receive state information from, some or all nearby balloons.Further, each balloon may relay state information that it receives froma nearby balloon to some or all nearby balloons. When all balloons doso, each balloon may be able to individually determine the state of thenetwork. Alternatively, certain balloons may be designated to aggregatestate information for a given portion of the network. These balloons maythen coordinate with one another to determine the overall state of thenetwork.

Further, in some aspects, control of a balloon network may be partiallyor entirely localized, such that it is not dependent on the overallstate of the network. For example, individual balloons may implementstation-keeping functions that only consider nearby balloons. Inparticular, each balloon may implement an energy function that takesinto account its own state and the states of nearby balloons. The energyfunction may be used to maintain and/or move to a desired position withrespect to the nearby balloons, without necessarily considering thedesired topology of the network as a whole. However, when each balloonimplements such an energy function for station-keeping, the balloonnetwork as a whole may maintain and/or move towards the desiredtopology.

As an example, each balloon A may receive distance information d₁ tod_(k) with respect to each of its k closest neighbors. Each balloon Amay treat the distance to each of the k balloons as a virtual springwith vector representing a force direction from the first nearestneighbor balloon i toward balloon A and with force magnitudeproportional to d_(i). The balloon A may sum each of the k vectors andthe summed vector is the vector of desired movement for balloon A.Balloon A may attempt to achieve the desired movement by controlling itsaltitude.

Alternatively, this process could assign the force magnitude of each ofthese virtual forces equal to d_(i)×d_(I), wherein d_(I) is proportionalto the distance to the second nearest neighbor balloon, for instance.

In another embodiment, a similar process could be carried out for eachof the k balloons and each balloon could transmit its planned movementvector to its local neighbors. Further rounds of refinement to eachballoon's planned movement vector can be made based on the correspondingplanned movement vectors of its neighbors. It will be evident to thoseskilled in the art that other algorithms could be implemented in aballoon network in an effort to maintain a set of balloon spacingsand/or a specific network capacity level over a given geographiclocation.

2d) Example Balloon Configuration

Various types of balloon systems may be incorporated in an exampleballoon network. As noted above, an example embodiment may utilizehigh-altitude balloons, which could typically operate in an altituderange between 17 km and 25 km. FIG. 3 shows a high-altitude balloon 300,according to an example embodiment. As shown, the balloon 300 includesan envelope 302, a skirt 304, a payload 306, and a cut-down system 308,which is attached between the balloon 302 and payload 304.

The envelope 302 and skirt 304 may take various forms, which may becurrently well-known or yet to be developed. For instance, the envelope302 and/or skirt 304 may be made of a highly-flexible latex material ormay be made of a rubber material such as chloroprene. In one exampleembodiment, the envelope and/or skirt could be made of metalized Mylaror BoPet. Other materials are also possible. Further, the shape and sizeof the envelope 302 and skirt 304 may vary depending upon the particularimplementation. Additionally, the envelope 302 may be filled withvarious different types of gases, such as helium and/or hydrogen. Othertypes of gases are possible as well.

The payload 306 of balloon 300 may include a processor 312 and on-boarddata storage, such as memory 314. The memory 314 may take the form of orinclude a non-transitory computer-readable medium. The non-transitorycomputer-readable medium may have instructions stored thereon, which canbe accessed and executed by the processor 312 in order to carry out theballoon functions described herein.

The payload 306 of balloon 300 may also include various other types ofequipment and systems to provide a number of different functions. Forexample, payload 306 may include optical communication system 316, whichmay transmit optical signals via an ultra-bright LED system 320, andwhich may receive optical signals via an optical-communication receiver322 (e.g., a photodiode receiver system). Further, payload 306 mayinclude an RF communication system 318, which may transmit and/orreceive RF communications via an antenna system 340.

The payload 306 may also include a power supply 326 to supply power tothe various components of balloon 300. The power supply 326 couldinclude a rechargeable battery. In other embodiments, the power supply326 may additionally or alternatively represent other means known in theart for producing power. In addition, the balloon 300 may include asolar power generation system 327. The solar power generation system 327may include solar panels and could be used to generate power thatcharges and/or is distributed by power supply 326.

Further, payload 306 may include various types of other systems andsensors 328. For example, payload 306 may include one or more videoand/or still cameras, a GPS system, various motion sensors (e.g.,accelerometers, magnetometers, gyroscopes, and/or compasses), and/orvarious sensors for capturing environmental data. Further, some or allof the components within payload 306 may be implemented in a radiosondeor other probe, which may be operable to measure, e.g., pressure,altitude, geographical position (latitude and longitude), temperature,relative humidity, and/or wind speed and/or wind direction, among otherinformation.

As noted, balloon 300 includes an ultra-bright LED system 320 forfree-space optical communication with other balloons. As such, opticalcommunication system 316 may be configured to transmit a free-spaceoptical signal by modulating the ultra-bright LED system 320. Theoptical communication system 316 may be implemented with mechanicalsystems and/or with hardware, firmware, and/or software. Generally, themanner in which an optical communication system is implemented may vary,depending upon the particular application. The optical communicationsystem 316 and other associated components are described in furtherdetail below.

In a further aspect, balloon 300 may be configured for altitude control.For instance, balloon 300 may include a variable buoyancy system, whichis configured to change the altitude of the balloon 300 by adjusting thevolume and/or density of the gas in the balloon 300. A variable buoyancysystem may take various forms, and may generally be any system that canchange the volume and/or density of gas in the envelope 302.

In an example embodiment, a variable buoyancy system may include abladder 310 that is located inside of envelope 302. The bladder 310could be an elastic chamber configured to hold liquid and/or gas.Alternatively, the bladder 310 need not be inside the envelope 302. Forinstance, the bladder 310 could be a ridged bladder that could bepressurized well beyond neutral pressure. The buoyancy of the balloon300 may therefore be adjusted by changing the density and/or volume ofthe gas in bladder 310. To change the density in bladder 310, balloon300 may be configured with systems and/or mechanisms for heating and/orcooling the gas in bladder 310. Further, to change the volume, balloon300 may include pumps or other features for adding gas to and/orremoving gas from bladder 310. Additionally or alternatively, to changethe volume of bladder 310, balloon 300 may include release valves orother features that are controllable to allow gas to escape from bladder310. Multiple bladders 310 could be implemented within the scope of thisdisclosure. For instance, multiple bladders could be used to improveballoon stability.

In an example embodiment, the envelope 302 could be filled with helium,hydrogen or other lighter-than-air material. The envelope 302 could thushave an associated upward buoyancy force. In such an embodiment, air inthe bladder 310 could be considered a ballast tank that may have anassociated downward ballast force. In another example embodiment, theamount of air in the bladder 310 could be changed by pumping air (e.g.,with an air compressor) into and out of the bladder 310. By adjustingthe amount of air in the bladder 310, the ballast force may becontrolled. In some embodiments, the ballast force may be used, in part,to counteract the buoyancy force and/or to provide altitude stability.

In another embodiment, a portion of the envelope 302 could be a firstcolor (e.g., black) and/or a first material from the rest of envelope302, which may have a second color (e.g., white) and/or a secondmaterial. For instance, the first color and/or first material could beconfigured to absorb a relatively larger amount of solar energy than thesecond color and/or second material. Thus, rotating the balloon suchthat the first material is facing the sun may act to heat the envelope302 as well as the gas inside the envelope 302. In this way, thebuoyancy force of the envelope 302 may increase. By rotating the balloonsuch that the second material is facing the sun, the temperature of gasinside the envelope 302 may decrease. Accordingly, the buoyancy forcemay decrease. In this manner, the buoyancy force of the balloon could beadjusted by changing the temperature/volume of gas inside the envelope302 using solar energy. In such embodiments, it is possible that abladder 310 may not be a necessary element of balloon 300. Thus, variouscontemplated embodiments, altitude control of balloon 300 could beachieved, at least in part, by adjusting the rotation of the balloonwith respect to the sun.

Further, a balloon 306 may include a navigation system (not shown). Thenavigation system may implement station-keeping functions to maintainposition within and/or move to a position in accordance with a desiredtopology. In particular, the navigation system may use altitudinal winddata to determine altitudinal adjustments that result in the windcarrying the balloon in a desired direction and/or to a desiredlocation. The altitude-control system may then make adjustments to thedensity of the balloon chamber in order to effectuate the determinedaltitudinal adjustments and cause the balloon to move laterally to thedesired direction and/or to the desired location. Alternatively, thealtitudinal adjustments may be computed by a ground-based orsatellite-based control system and communicated to the high-altitudeballoon. In other embodiments, specific balloons in a heterogeneousballoon network may be configured to compute altitudinal adjustments forother balloons and transmit the adjustment commands to those otherballoons.

As shown, the balloon 300 also includes a cut-down system 308. Thecut-down system 308 may be activated to separate the payload 306 fromthe rest of balloon 300. The cut-down system 308 could include at leasta connector, such as a balloon cord, connecting the payload 306 to theenvelope 302 and a means for severing the connector (e.g., a shearingmechanism or an explosive bolt). In an example embodiment, the ballooncord, which may be nylon, is wrapped with a nichrome wire. A currentcould be passed through the nichrome wire to heat it and melt the cord,cutting the payload 306 away from the envelope 302.

The cut-down functionality may be utilized anytime the payload needs tobe accessed on the ground, such as when it is time to remove balloon 300from a balloon network, when maintenance is due on systems withinpayload 306, and/or when power supply 326 needs to be recharged orreplaced.

In an alternative arrangement, a balloon may not include a cut-downsystem. In such an arrangement, the navigation system may be operable tonavigate the balloon to a landing location, in the event the balloonneeds to be removed from the network and/or accessed on the ground.Further, it is possible that a balloon may be self-sustaining, such thatit does not need to be accessed on the ground. In other embodiments,in-flight balloons may be serviced by specific service balloons oranother type of aerostat or aircraft.

In a further aspect, balloon 300 includes a gas-flow system, which maybe used for altitude control. In the illustrated example, the gas-flowsystem includes a high-pressure storage chamber 342, a gas-flow tube350, and a pump 348, which may be used to pump gas out of the envelope302, through the gas-flow tube 350, and into the high-pressure storagechamber 342. As such, balloon 300 may be configured to decrease itsaltitude by pumping gas out of envelope 302 and into high-pressurestorage chamber 342. Further, balloon 300 may be configured to move gasinto the envelope and increase its altitude by opening a valve 352 atthe end of gas-flow tube 350, and allowing lighter-than-air gas fromhigh-pressure storage chamber 342 to flow into envelope 302.

Note that the high-pressure storage chamber 342, in an example balloon,may be constructed such that its volume does not change due to, e.g.,the high forces and/or torques resulting from gas that is compressedwithin the chamber. In an example embodiment, the high-pressure storagechamber 342 may be made of a material with a high tensile-strength toweight ratio, such as titanium or a composite made of spun carbon fiberand epoxy. However, high-pressure storage chamber 342 may be made ofother materials or combinations of materials, without departing from thescope of the invention.

In a further aspect, balloon 300 may be configured to generate powerfrom gas flow out of high-pressure storage chamber 342 and into envelope302. For example, a turbine (not shown) may be fitted in the path of thegas flow (e.g., at the end of gas-flow tube 350). The turbine may be agas turbine generator, or may take other forms. Such a turbine maygenerate power when gas flows from high-pressure storage chamber 342 toenvelope 302. The generated power may be immediately used to operate theballoon and/or may be used to recharge the balloon's battery.

In a further aspect, a turbine, such as a gas turbine generator, mayalso be configured to operate “in reverse” in order to pump gas into andpressurize the high-pressure storage chamber 342. In such an embodiment,pump 348 may be unnecessary. However, an embodiment with a turbine couldalso include a pump.

In some embodiments, pump 348 may be a positive displacement pump, whichis operable to pump gas out of the envelope 302 and into high-pressurestorage chamber 342. Further, a positive-displacement pump may beoperable in reverse to function as a generator.

Further, in the illustrated example, the gas-flow system includes avalve 346, which is configured to adjust the gas-flow path betweenenvelope 302, high-pressure storage chamber 342, and fuel cell 344. Inparticular, valve 346 may adjust the gas-flow path such that gas canflow between high-pressure storage chamber 342 and envelope 302, andshut off the path to fuel cell 344. Alternatively, valve 346 may shutoff the path high-pressure storage chamber 342, and create a gas-flowpath such that gas can flow between fuel cell 344 and envelope 302.

Balloon 300 may be configured to operate fuel cell 344 in order toproduce power via the chemical reaction of hydrogen and oxygen toproduce water, and to operate fuel cell 344 in reverse so as to createhydrogen and oxygen from water. Accordingly, to increase its altitude,balloon 300 may run fuel cell 344 in reverse so as to generate gas(e.g., hydrogen gas), which can then be moved into the envelope toincrease buoyancy. Specifically, balloon may increase its altitude byrunning fuel cell 344 in reverse, adjusting valve 346 and valve 352 suchthat hydrogen gas produced by fuel cell 344 can flow from fuel cell 344,through gas-flow tube 350, and into envelope 302.

To run fuel cell 344 “in reverse,” balloon 300 may utilize anelectrolysis mechanism in order to separate water molecules. Forexample, a balloon may be configured to use a photocatalytic watersplitting technique to produce hydrogen and oxygen from water. Othertechniques for electrolysis are also possible.

Further, balloon 300 may be configured to separate the oxygen andhydrogen produced via electrolysis. To do so, the fuel cell 344 and/oranother balloon component may include an anode and cathode that attractthe positively and negatively charged O− and H− ions, and separate thetwo gases. Once the gases are separated, the hydrogen may be directedinto the envelope. Additionally or alternatively, the hydrogen and/oroxygen may be moved into the high-pressure storage chamber.

Further, to decrease its altitude, balloon 300 may use pump 348 to pumpgas from envelope 302 to the fuel cell 344, so that the hydrogen gas canbe consumed in the fuel cell's chemical reaction to produce power (e.g.,the chemical reaction of hydrogen and oxygen to create water). Byconsuming the hydrogen gas the buoyancy of the balloon may be reduced,which in turn may decrease the altitude of the balloon.

It should be understood that variations on the illustrated high-pressurestorage chamber are possible. For example, the high-pressure storagechamber may take on various sizes and/or shapes, and be constructed fromvarious materials, depending upon the implementation. Further, whilehigh-pressure storage chamber 342 is shown as part of payload 306,high-pressure storage chamber could also be located inside of envelope302. Yet further, a balloon could implement multiple high-pressurestorage chambers. Other variations on the illustrated high-pressurestorage chamber 342 are also possible.

It should also be understood that variations on the illustrated air-flowtube 350 are possible. Specifically, any configuration that facilitatesmovement of gas between the high-pressure storage chamber and theenvelope is possible.

Yet further, it should be understood that a balloon and/or componentsthereof may vary from the illustrated balloon 300. For example, some orall of the components of balloon 300 may be omitted. Components ofballoon 300 could also be combined. Further, a balloon may includeadditional components in addition or in the alternative to theillustrated components of balloon 300. Other variations are alsopossible.

3. BALLOON NETWORK WITH OPTICAL AND RF LINKS BETWEEN BALLOONS

In some embodiments, a high-altitude-balloon network may includesuper-node balloons, which communicate with one another via opticallinks, as well as sub-node balloons, which communicate with super-nodeballoons via RF links. Generally, the optical links between super-nodeballoons may be configured to have more bandwidth than the RF linksbetween super-node and sub-node balloons. As such, the super-nodeballoons may function as the backbone of the balloon network, while thesub-nodes may provide sub-networks providing access to the balloonnetwork and/or connecting the balloon network to other networks.

FIG. 4 is a simplified diagram illustrating a balloon network thatincludes super-nodes and sub-nodes, according to an example embodiment.More specifically, FIG. 4 illustrates a portion of a balloon network 400that includes super-node balloons 410A to 410C (which may also bereferred to as “super-nodes”) and sub-node balloons 420 (which may alsobe referred to as “sub-nodes”).

Each super-node balloon 410A to 410C may include a free-space opticalcommunication system that is operable for packet-data communication withother super-node balloons. As such, super-nodes may communicate with oneanother over optical links. For example, in the illustrated embodiment,super-node 410A and super-node 401B may communicate with one anotherover optical link 402, and super-node 410A and super-node 401C maycommunicate with one another over optical link 404.

Each of the sub-node balloons 420 may include a radio-frequency (RF)communication system that is operable for packet-data communication overone or more RF air interfaces. Accordingly, each super-node balloon 410Ato 410C may include an RF communication system that is operable to routepacket data to one or more nearby sub-node balloons 420. When a sub-node420 receives packet data from a super-node 410, the sub-node 420 may useits RF communication system to route the packet data to a ground-basedstation 430 via an RF air interface.

As noted above, the super-nodes 410A to 410C may be configured for bothlonger-range optical communication with other super-nodes andshorter-range RF communications with nearby sub-nodes 420. For example,super-nodes 410A to 410C may use using high-power or ultra-bright LEDsto transmit optical signals over optical links 402, 404, which mayextend for as much as 100 miles, or possibly more. Configured as such,the super-nodes 410A to 410C may be capable of optical communications atspeeds of 10 to 50 GB/sec or more.

A larger number of balloons may be configured as sub-nodes, which maycommunicate with ground-based Internet nodes at speeds on the order ofapproximately 10 MB/sec. Configured as such, the sub-nodes 420 may beconfigured to connect the super-nodes 410 to other networks and/or toclient devices.

Note that the data speeds and link distances described in the aboveexample and elsewhere herein are provided for illustrative purposes andshould not be considered limiting; other data speeds and link distancesare possible.

In some embodiments, the super-nodes 410A to 410C may function as a corenetwork, while the sub-nodes 420 function as one or more access networksto the core network. In such an embodiment, some or all of the sub-nodes420 may also function as gateways to the balloon network 400.Additionally or alternatively, some or all of ground-based stations 430may function as gateways to the balloon network 400.

4. EXAMPLE APEX FITTING

The present embodiments advantageously provide an apex fitting 500 thatmay reduce air leaks from and stress on a balloon envelope. FIGS. 5A to7 show an apex fitting 500 that includes a base plate 510 having a topsurface 511 and a bottom surface 512. The base plate 510 may define anopening 515. In a preferred embodiment, the opening 515 of the baseplate 510 may be centered in the base plate 510. The opening mayalternatively be located off-center within the base plate 510. The baseplate 510 may further be configured to be securable to an exterior of aballoon envelope 520 via a single opening 521 in the balloon envelope520, as described in more detail below. In addition, the base plate 510may be made from a strong lightweight material, such as aluminum orsteel, engineered plastics or composite materials, among otherpossibilities. In various embodiments, the base plate 510 has a diameterranging from about 15 inches to about 30 inches. As used herein, “about”means ±5%.

At least one stud 525 may be coupled to the base plate 510. In apreferred embodiment, a plurality of studs 525 may be coupled to thebase plate 510. Each stud 525 may further be configured to be securableto a tendon 530. For example, a tendon 530 may be looped about acorresponding stud 525. In another preferred embodiment, the pluralityof studs 525 may have a spaced-apart arrangement about a periphery ofthe base plate 510 to substantially evenly distribute the tendons 530about the periphery of the balloon envelope 520. Further, in oneembodiment, each stud 525 may include a body 527 and a flange 526coupled to the body at a free end. In one embodiment, the flange 526 maycomprise a nut with threads defined on an interior surface that may bejoined to a stud 525 via mating threads defined on the exterior of thestud 525 at the free end.

The apex fitting 500 may further include a retention ring 535. Theretention ring 535 may be used to hold the tendons 530 looped in placeover the studs 525. For example, the retention ring 535 may define atleast one opening 540 that may be configured to receive a correspondingstud 525. In a preferred embodiment, a plurality of openings 540 aredefined in the retention ring 535. In one embodiment, the openings 540of the retention ring 535 may have a first portion 541 sized to receivethe flange 526 of a corresponding stud 525 and a second portion 542defining a channel or slot having a width that is less than a diameterof the flange 526 of the corresponding stud 525. Further, the secondportion 542 of the opening 540 may be configured to receive the body 527of a corresponding stud. This arrangement allows the retention ring tobe rotated relative to the base plate 510 and locked into place. In thislocked position, the flange 526 of each stud 525 is aligned over thechannel or slot of the second portion 542 of opening 540, preventing theremoval of the retention ring 535 from the base plate 510. In a furtherembodiment, the second portion 542 of the openings 540 may each beconfigured as a detent that is capable of retaining the body 527 of acorresponding stud 525 once the retention ring 535 has been rotated intothe locked position. In various embodiments, the retention ring 535 maybe made from a strong lightweight material, such as aluminum or steel,among other possibilities.

In one embodiment, the apparatus further includes at least one lockingpin 550 disposed through the retention ring 535 to hold the retentionring 535 in the locked position. In a preferred embodiment, the at leastone locking pin 550 includes a plurality of locking pins 550. In variousembodiments, the locking pins 550 may include retention screws, rivetsor bolts, among others possibilities, disposed through the retentionring 535 and coupled to a fitting 551 in the base plate 510. In variousother embodiments, the locking pins 550 may comprise pins or plugs, forexample, disposed through the first portion 541 of the plurality ofopenings 540 of the retention ring 535.

The apex fitting 500 may also include a fill-port body 545 defining acavity. A flange 546 may be coupled to the fill-port body 545. Theflange 546 is preferably located at or near a base of the fill-port body545. The fill-port body 545 may be arranged coaxially with and extendthrough the opening 515 of the base plate 510 such that the flange 546lies adjacent to the bottom surface 512 of the base plate 510. Inaddition, a locking body 547 may be coupled to the fill-port body 545 tohold the flange 546 against the base plate 510 and/or the balloonenvelope 520 (as described below). The locking body 547 may furtherdefine an opening arranged coaxially with the fill-port body 545. Thefill-port body 545 may extend through the opening of the locking body547 such that a portion 548 of the locking body 547 lies adjacent to thetop surface 511 of the base plate 510. In one embodiment, the lockingbody 547 may be press-fit onto the fill-port body 545 such that thelocking body 547 is received in a detent 549 defined by the fill-portbody 545. In another embodiment, the locking body 547 may be press-fitonto the fill-port body 545 such that at least one detent (not shown)defined on the locking body 547 receives at least one protuberance (notshown) coupled to the fill-port body 545. In a further embodiment, thelocking body 545 may be coupled to the base plate 510 or the fill-portbody 545 via one or more connectors, such as screws 544 or rivets. Inyet another embodiment, the locking body 547 may be coupled to the baseplate 510 or the fill-port body 545 via adhesive. In a furtherembodiment, the locking body 547 may include threads (not shown) definedalong the opening of the locking body 547, and the fill-port body 545may include mating threads (not shown) defined along an exterior of thefill-port body 545, such that the locking body 547 may be screwed ontothe fill-port body 545. Still other possibilities exist to couple to thelocking body 547 to the fill-port body 545 or the base plate withoutcreating additional perforations in the balloon envelope 520.

In one embodiment, the apex fitting 500 further includes a balloonenvelope 520. The balloon envelope 520 may define an opening 521 at anapex 522 of the balloon envelope 520. The fill-port body 545 may extendthrough the opening 521 of the balloon envelope 520 such that a portion523 of the balloon envelope 520 may be disposed between the flange 546of the fill-port body 545 and the bottom surface 512 of the base plate510. In a further embodiment, a gasket (not shown) may be disposedbetween the flange 546 of the fill-port body 545 and the balloonenvelope 520. The purpose of the gasket is to minimize stress on theopening 521 of the balloon envelope 520 and to create a more effectiveseal between the base plate 510 and the balloon envelope 520.

In one embodiment, the base plate 510 may define one or more apertures513. In this embodiment, the aperture(s) 513 may take many forms,including a polygonal, a circular or a half moon shape, among otherpossibilities. In one embodiment, the base plate 510 may include asingle aperture (not shown). In another embodiment, the base plate 510may include a plurality of apertures 513. In further embodiment, shownin FIG. 5A, a plurality of apertures 513 are arranged such that the baseplate 510 has a spoke-like configuration.

In another embodiment, the apex fitting 500 may further include a flighttermination system (not shown) that is configured to puncture theballoon envelope 520 through at least one aperture 513 of the base plate510. The flight termination system is of a type known in the art and isconfigured to vent lift gas by puncturing the balloon envelope 520.

In one embodiment, one or more electrical passages are disposed througha cap 555, where the cap 555 may be removably coupled to the fill-portbody 545. These electrical passages may be configured to be coupled toone or more sensors, for example. In one embodiment, these one or moresensors (not shown) may be coupled to the balloon envelope 520 andaligned with at least one of the apertures 513 of the base plate 510. Inanother embodiment, inductive power and data transfer may be utilizedwith the one or more sensors via one or more of the apertures 513. Thesensor(s) may be configured to measure any number of parameters, forexample, temperature, air pressure, lift gas purity or moisture, amongother possibilities.

5. ILLUSTRATIVE METHODS

FIG. 8 is a flow chart of a method, according to an example embodiment.Example methods, such as method 800 of FIG. 8, may be carried out by ahuman operator or a control system for automated manufacturing. Acontrol system may take the form of program instructions stored on anon-transitory computer readable medium and a processor that executesthe instructions. However, a control system may take other formsincluding software, hardware, and/or firmware. Example methods may beimplemented as part of the manufacturing or maintenance process for aballoon.

As shown by block 810, method 800 involves providing affixing a baseplate to a balloon envelope, where the balloon envelope defines anopening at an apex of the balloon envelope, where the base plate definesan opening, where the opening of the base plate is aligned with theopening of the balloon envelope, and where a plurality of studs arecoupled to the base plate. Then at block 820, a fill-port body may beplaced through the opening of the balloon envelope and through theopening of the base plate such that a flange of the fill-port body liesadjacent to the balloon envelope. A locking body may then be secured tothe fill-port body and/or the base plate, at block 830, such that thelocking body lies adjacent to the base plate. At block 840, a pluralityof tendons may be secured to the plurality of studs. Then, at block 850,a retention ring may be secured to the base plate.

In one embodiment, securing the retention ring to the base plate mayinclude (i) aligning the first portion of the plurality of openings inthe retention ring with the plurality of studs on the base plate, (ii)sliding the retention ring over the flanges of the plurality of studssuch that the flanges of the plurality of studs extend through the firstportion of the plurality of openings of the retention ring and (iii)rotating the retention ring relative to the base plate such that a bodyof each of the plurality of studs are received within the second portionof the plurality of openings of the retention ring. In a furtherembodiment, securing the retention ring to the base plate also includescoupling at least one locking pin to the retention ring.

In another embodiment, securing the lock body to the fill-port bodyand/or the base plate may include (i) press-fitting the locking bodyonto the fill-port body such that the locking body is received in adetent defined by the fill-port body, (ii) press-fitting the lockingbody onto the fill-port body such that at least one detent defined onthe locking body receives at least one protuberance defined on thefill-port body, (iii) coupling the locking body to the base plate or thefill-port body via one or more connectors, (iv) coupling the lockingbody to the base plate or the fill-port body via adhesive, and/or (v)screwing the lock nut onto the fill-port body via threads coupled to theopening of the locking body and mating threads coupled to an exterior ofthe fill-port body, among other possibilities.

6. CONCLUSION

The above detailed description describes various features and functionsof the disclosed systems, devices, and methods with reference to theaccompanying figures. While various aspects and embodiments have beendisclosed herein, other aspects and embodiments will be apparent tothose skilled in the art. The various aspects and embodiments disclosedherein are for purposes of illustration and are not intended to belimiting, with the true scope and spirit being indicated by thefollowing claims.

1. An apparatus, comprising: a base plate having a top surface and abottom surface, wherein the base plate defines an opening, and whereinthe base plate is configured to be securable to an exterior of a balloonenvelope; a plurality of studs coupled to the base plate, wherein theplurality of studs are configured to be securable to a tendon, whereineach of the plurality of studs have a body with a flange coupled to afree end of the body; a retention ring defining a plurality of openingseach configured to receive one of the plurality of studs.
 2. Theapparatus of claim 1, further comprising: a fill-port body defining acavity, wherein a flange is coupled to the fill-port body, wherein thefill-port body is arranged coaxially with and extends through theopening of the base plate such that the flange lies adjacent to thebottom surface of the base plate.
 3. The apparatus of claim 2, furthercomprising: a locking body coupled to the fill-port body, wherein thelocking body defines an opening arranged coaxially with the fill-portbody, wherein the fill-port body extends through the opening of thelocking body such that a portion of the locking body lies adjacent tothe top surface of the base plate.
 4. The apparatus of claim 1, whereinthe base plate defines one or more apertures.
 5. The apparatus of claim1, further comprising: at least one locking pin disposed through theretention ring.
 6. The apparatus of claim 5, wherein the at least onelocking pin may comprise two or more retention screws disposed throughthe retention ring and coupled to the base plate.
 7. The apparatus ofclaim 1, wherein the opening of the base plate is centered in the baseplate.
 8. The apparatus of claim 2, further comprising: a balloonenvelope, wherein the balloon envelope defines an opening at an apex ofthe balloon envelope, wherein the body of the fill port extends throughthe opening of the balloon envelope such that a portion of the balloonenvelope is disposed between the flange of the fill-port body and thebottom surface of the base plate.
 9. The apparatus of claim 8, wherein agasket is disposed between the flange of the fill-port body and theballoon envelope.
 10. The apparatus of claim 8, wherein one or moreelectrical passages are disposed through a cap removably coupled to thefill-port body.
 11. The apparatus of claim 8, wherein the base platedefines one or more apertures.
 12. The apparatus of claim 11, furthercomprising: one or more sensors coupled to the balloon envelope andaligned with at least one of the one or more apertures of the baseplate.
 13. The apparatus of claim 11, further comprising: a flighttermination system configured to puncture the balloon envelope throughat least one of the one or more apertures of the base plate.
 14. Theapparatus of claim 11, wherein the one or more apertures of the baseplate comprises one aperture, wherein the aperture has a half moonshape.
 15. The apparatus of claim 11, wherein the one or more aperturesof the base plate comprises a plurality of apertures, wherein theplurality of apertures are arranged such that the base plate has aspoke-like configuration.
 16. The apparatus of claim 1, wherein theplurality of studs have a spaced-apart arrangement about a periphery ofthe base plate.
 17. A method, comprising: affixing a base plate to aballoon envelope, wherein the balloon envelope defines an opening at anapex of the balloon envelope, wherein the base plate defines an opening,wherein the opening of the base plate is aligned with the opening of theballoon envelope, and wherein a plurality of studs are coupled to thebase plate, wherein each of the plurality of studs have a body with aflange coupled to a free end of the body; securing a plurality oftendons to the plurality of studs; and securing a retention ring to thebase plate, wherein the retention ring defines a plurality of openingseach configured to receive one of the plurality of studs, wherein eachof the plurality of openings of the retention ring has a first portionsized to receive the flange of one of the plurality of studs, whereineach of the plurality of openings of the retention ring has a secondportion defining a channel having a width that is less than a diameterof the flange of one of the plurality of studs.
 18. The method of claim17, wherein securing the retention ring to the base plate comprises (i)aligning the first portion of the plurality of openings in the retentionring with the plurality of studs of the base plate, (ii) sliding theretention ring over the flanges of the plurality of studs such that theflanges of the plurality of studs extend through the first portion ofthe plurality of openings of the retention ring and (iii) rotating theretention ring relative to the base plate such that a body of each ofthe plurality of studs are received within the second portion of theplurality of openings of the retention ring.
 19. The method of claim 18,wherein securing the retention ring to the base plate further comprisescoupling at least one locking pin to the retention ring.
 20. The methodof claim 17, further comprising: placing a fill-port body through theopening of the balloon envelope and through the opening of the baseplate such that a flange of the fill-port body lies adjacent to theballoon envelope and opposite a bottom surface of the base plate; andsecuring a locking body to the fill-port body, the base plate, or boththe fill-port body and the base plate such that the locking body liesadjacent to a top surface of the base plate, wherein securing thelocking body to the fill-port body, the base plate, or both comprises(i) press-fitting the locking body onto the fill-port body such that thelocking body is received in a detent defined by the fill-port body, (ii)press-fitting the locking body onto the fill-port body such that atleast one detent defined on the locking body receives at least oneprotuberance coupled to the fill-port body, (iii) coupling the lockingbody to the base plate or the fill-port body via one or more connectors,(iv) coupling the locking body to the base plate or the fill-port bodyvia adhesive, or (v) screwing a lock nut onto the fill-port body viathreads coupled to the opening of the locking body and mating threadscoupled to an exterior of the fill-port body.